Fair Value Measurements - Additional Information (Detail) $ in Millions		12 Months Ended
		Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Deferred fees		$ 2	$ 1
Revaluation period		90 days
Unfunded commitments, equity securities measured at net asset value		$ 72	43
Derivative financial assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of level 3 assets		179	301
Derivative financial liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of level 3 liabilities	[1]	213	152
Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of level 3 assets		2,088	2,207	$ 3,356
Fair value of level 3 liabilities		1,337	1,538	1,906
Fair Value Assets, Transfers Into Level 3		106	4
Fair Value Assets, Transfers Out of Level 3		21	1
Fair Value Liability, Transfers Into Level 3		29	43
Fair Value Liability, Transfers Out of Level 3		365	362
Level 3 [Member] | Foreign exchange contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of level 3 assets	[2]	(1)	0	0
Fair Value Assets, Transfers Into Level 3	[2]	0	0
Fair Value Assets, Transfers Out of Level 3	[2]	0	0
Level 3 [Member] | Equity contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of level 3 assets	[2]	(52)	81	(2)
Fair Value Assets, Transfers Into Level 3	[2]	(2)	4
Fair Value Assets, Transfers Out of Level 3	[2]	21	1
Collateralized debt obligations [Member] | Level 3 [Member] | Trading assets, excluding derivatives [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of level 3 assets	[3]	100	129	184
Fair Value Assets, Transfers Into Level 3	[3]	0	0
Fair Value Assets, Transfers Out of Level 3	[3]	0	0
Domestic Deposits [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of level 3 liabilities	[1]	925	897	1,407
Fair Value Liability, Transfers Into Level 3	[1]	28	31
Fair Value Liability, Transfers Out of Level 3	[1]	206	260
Borrowings [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of level 3 liabilities	[1]	412	641	$ 499
Fair Value Liability, Transfers Into Level 3	[1]	1	12
Fair Value Liability, Transfers Out of Level 3	[1]	159	102
Residential Mortgage Backed Securities [Member] | Level 3 [Member] | Trading assets, excluding derivatives [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of level 3 assets	[3]	16	0
Fair Value Assets, Transfers Into Level 3		16
Fair Value Assets, Transfers Out of Level 3	[3]	0
Student loan asset-backed securities [Member] | Level 3 [Member] | Trading assets, excluding derivatives [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of level 3 assets		92	0
Fair Value Assets, Transfers Into Level 3		92
Fair Value Assets, Transfers Out of Level 3		0
Unfunded Loan Commitment [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Deferred fees		$ 165	$ 158
Measurement Input, Prepayment Rates [Member] | Fair Value, Measurements, Recurring [Member] | Collateralized debt obligations [Member] | Valuation Technique, Consensus Pricing Model [Member] | Minimum [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Debt Securities, Trading, Measurement Input		0.00	0.00
Measurement Input, Prepayment Rates [Member] | Fair Value, Measurements, Recurring [Member] | Collateralized debt obligations [Member] | Valuation Technique, Consensus Pricing Model [Member] | Maximum [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Debt Securities, Trading, Measurement Input		0.01	0.06
Measurement Input, Prepayment Rates [Member] | Fair Value, Measurements, Recurring [Member] | Collateralized debt obligations [Member] | Valuation Technique, Consensus Pricing Model [Member] | Weighted Average [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Debt Securities, Trading, Measurement Input		0.004
Measurement Input, Prepayment Rates [Member] | Fair Value, Measurements, Recurring [Member] | Residential Mortgage Backed Securities [Member] | Valuation Technique, Consensus Pricing Model [Member] | Minimum [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Debt Securities, Trading, Measurement Input		0.00
Measurement Input, Prepayment Rates [Member] | Fair Value, Measurements, Recurring [Member] | Residential Mortgage Backed Securities [Member] | Valuation Technique, Consensus Pricing Model [Member] | Maximum [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Debt Securities, Trading, Measurement Input		0.05
Measurement Input, Prepayment Rates [Member] | Fair Value, Measurements, Recurring [Member] | Residential Mortgage Backed Securities [Member] | Valuation Technique, Consensus Pricing Model [Member] | Weighted Average [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Debt Securities, Trading, Measurement Input		0.025
Measurement Input, Prepayment Rates [Member] | Fair Value, Measurements, Recurring [Member] | Student loan asset-backed securities [Member] | Valuation Technique, Consensus Pricing Model [Member] | Minimum [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Debt Securities, Trading, Measurement Input		0.06
Measurement Input, Prepayment Rates [Member] | Fair Value, Measurements, Recurring [Member] | Student loan asset-backed securities [Member] | Valuation Technique, Consensus Pricing Model [Member] | Maximum [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Debt Securities, Trading, Measurement Input		0.07
Measurement Input, Prepayment Rates [Member] | Fair Value, Measurements, Recurring [Member] | Student loan asset-backed securities [Member] | Valuation Technique, Consensus Pricing Model [Member] | Weighted Average [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Debt Securities, Trading, Measurement Input		0.063
Measurement Input, Default Rate [Member] | Fair Value, Measurements, Recurring [Member] | Collateralized debt obligations [Member] | Valuation Technique, Consensus Pricing Model [Member] | Minimum [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Debt Securities, Trading, Measurement Input		0.00	0.04
Measurement Input, Default Rate [Member] | Fair Value, Measurements, Recurring [Member] | Collateralized debt obligations [Member] | Valuation Technique, Consensus Pricing Model [Member] | Maximum [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Debt Securities, Trading, Measurement Input		0.01	0.06
Measurement Input, Default Rate [Member] | Fair Value, Measurements, Recurring [Member] | Collateralized debt obligations [Member] | Valuation Technique, Consensus Pricing Model [Member] | Weighted Average [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Debt Securities, Trading, Measurement Input		0.009
Measurement Input, Default Rate [Member] | Fair Value, Measurements, Recurring [Member] | Residential Mortgage Backed Securities [Member] | Valuation Technique, Consensus Pricing Model [Member] | Minimum [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Debt Securities, Trading, Measurement Input		0.01
Measurement Input, Default Rate [Member] | Fair Value, Measurements, Recurring [Member] | Residential Mortgage Backed Securities [Member] | Valuation Technique, Consensus Pricing Model [Member] | Maximum [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Debt Securities, Trading, Measurement Input		0.04
Measurement Input, Default Rate [Member] | Fair Value, Measurements, Recurring [Member] | Residential Mortgage Backed Securities [Member] | Valuation Technique, Consensus Pricing Model [Member] | Weighted Average [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Debt Securities, Trading, Measurement Input		0.020
Measurement Input, Default Rate [Member] | Fair Value, Measurements, Recurring [Member] | Student loan asset-backed securities [Member] | Valuation Technique, Consensus Pricing Model [Member] | Minimum [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Debt Securities, Trading, Measurement Input		0.01
Measurement Input, Default Rate [Member] | Fair Value, Measurements, Recurring [Member] | Student loan asset-backed securities [Member] | Valuation Technique, Consensus Pricing Model [Member] | Maximum [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Debt Securities, Trading, Measurement Input		0.02
Measurement Input, Default Rate [Member] | Fair Value, Measurements, Recurring [Member] | Student loan asset-backed securities [Member] | Valuation Technique, Consensus Pricing Model [Member] | Weighted Average [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Debt Securities, Trading, Measurement Input		0.017
Measurement Input, Implied Volatility of Currency Pairs [Member] | Fair Value, Measurements, Recurring [Member] | Valuation Technique, Option Pricing Model [Member] | Foreign exchange contracts [Member] | Minimum [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Derivative Asset (Liability) Net, Measurement Input	[4]	0.08	0.06
Measurement Input, Implied Volatility of Currency Pairs [Member] | Fair Value, Measurements, Recurring [Member] | Valuation Technique, Option Pricing Model [Member] | Foreign exchange contracts [Member] | Maximum [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Derivative Asset (Liability) Net, Measurement Input	[4]	0.12	0.09
Measurement Input, Implied Volatility of Currency Pairs [Member] | Fair Value, Measurements, Recurring [Member] | Valuation Technique, Option Pricing Model [Member] | Foreign exchange contracts [Member] | Weighted Average [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Derivative Asset (Liability) Net, Measurement Input	[4]	0.06
Measurement Input, Loss Severity Rates [Member] | Residential Mortgage [Member] | Weighted Average [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Loans Held-for-sale, Measurement Input		0.70
Measurement Input, Loss Severity Rates [Member] | Impaired commercial loans [Member] | Weighted Average [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Loans Held-for-sale, Measurement Input		0.36
Measurement Input, Loss Severity Rates [Member] | Fair Value, Measurements, Recurring [Member] | Collateralized debt obligations [Member] | Valuation Technique, Consensus Pricing Model [Member] | Minimum [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Debt Securities, Trading, Measurement Input		0.90	0.55
Measurement Input, Loss Severity Rates [Member] | Fair Value, Measurements, Recurring [Member] | Collateralized debt obligations [Member] | Valuation Technique, Consensus Pricing Model [Member] | Maximum [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Debt Securities, Trading, Measurement Input		0.95	0.60
Measurement Input, Loss Severity Rates [Member] | Fair Value, Measurements, Recurring [Member] | Collateralized debt obligations [Member] | Valuation Technique, Consensus Pricing Model [Member] | Weighted Average [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Debt Securities, Trading, Measurement Input		0.930
Measurement Input, Loss Severity Rates [Member] | Fair Value, Measurements, Recurring [Member] | Residential Mortgage Backed Securities [Member] | Valuation Technique, Consensus Pricing Model [Member] | Minimum [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Debt Securities, Trading, Measurement Input		0.80
Measurement Input, Loss Severity Rates [Member] | Fair Value, Measurements, Recurring [Member] | Residential Mortgage Backed Securities [Member] | Valuation Technique, Consensus Pricing Model [Member] | Maximum [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Debt Securities, Trading, Measurement Input		0.85
Measurement Input, Loss Severity Rates [Member] | Fair Value, Measurements, Recurring [Member] | Residential Mortgage Backed Securities [Member] | Valuation Technique, Consensus Pricing Model [Member] | Weighted Average [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Debt Securities, Trading, Measurement Input		0.825
Measurement Input, Loss Severity Rates [Member] | Fair Value, Measurements, Recurring [Member] | Student loan asset-backed securities [Member] | Valuation Technique, Consensus Pricing Model [Member] | Minimum [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Debt Securities, Trading, Measurement Input		0.25
Measurement Input, Loss Severity Rates [Member] | Fair Value, Measurements, Recurring [Member] | Student loan asset-backed securities [Member] | Valuation Technique, Consensus Pricing Model [Member] | Maximum [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Debt Securities, Trading, Measurement Input		0.40
Measurement Input, Loss Severity Rates [Member] | Fair Value, Measurements, Recurring [Member] | Student loan asset-backed securities [Member] | Valuation Technique, Consensus Pricing Model [Member] | Weighted Average [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Debt Securities, Trading, Measurement Input		0.360
Measurement Input, Discount Margin [Member] | Fair Value, Measurements, Recurring [Member] | Residential Mortgage Backed Securities [Member] | Valuation Technique, Consensus Pricing Model [Member] | Minimum [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Debt Securities, Trading, Measurement Input		0.0100
Measurement Input, Discount Margin [Member] | Fair Value, Measurements, Recurring [Member] | Residential Mortgage Backed Securities [Member] | Valuation Technique, Consensus Pricing Model [Member] | Maximum [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Debt Securities, Trading, Measurement Input		0.0250
Measurement Input, Discount Margin [Member] | Fair Value, Measurements, Recurring [Member] | Residential Mortgage Backed Securities [Member] | Valuation Technique, Consensus Pricing Model [Member] | Weighted Average [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Debt Securities, Trading, Measurement Input		0.0175
Measurement Input, Discount Margin [Member] | Fair Value, Measurements, Recurring [Member] | Student loan asset-backed securities [Member] | Valuation Technique, Consensus Pricing Model [Member] | Minimum [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Debt Securities, Trading, Measurement Input		0.0091
Measurement Input, Discount Margin [Member] | Fair Value, Measurements, Recurring [Member] | Student loan asset-backed securities [Member] | Valuation Technique, Consensus Pricing Model [Member] | Maximum [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Debt Securities, Trading, Measurement Input		0.0115
Measurement Input, Discount Margin [Member] | Fair Value, Measurements, Recurring [Member] | Student loan asset-backed securities [Member] | Valuation Technique, Consensus Pricing Model [Member] | Weighted Average [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Debt Securities, Trading, Measurement Input		0.0097
Measurement Input, Equity / Equity Index Volatility [Member] | Fair Value, Measurements, Recurring [Member] | Valuation Technique, Option Pricing Model [Member] | Equity contracts [Member] | Minimum [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Derivative Asset (Liability) Net, Measurement Input	[4]	0.07	0.07
Measurement Input, Equity / Equity Index Volatility [Member] | Fair Value, Measurements, Recurring [Member] | Valuation Technique, Option Pricing Model [Member] | Equity contracts [Member] | Maximum [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Derivative Asset (Liability) Net, Measurement Input	[4]	0.44	0.42
Measurement Input, Equity / Equity Index Volatility [Member] | Fair Value, Measurements, Recurring [Member] | Valuation Technique, Option Pricing Model [Member] | Equity contracts [Member] | Weighted Average [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Derivative Asset (Liability) Net, Measurement Input	[4]	0.10

[1] Excluding unrealized gains (losses) on fair value option liabilities attributable to our own credit spread, which are recorded in other comprehensive income (loss), gains (losses) on fair value option liabilities are included in gain (loss) on instruments designated at fair value and related derivatives in the consolidated statement of income (loss).

[2] Level 3 net derivatives included derivative assets of $179 million and derivative liabilities of $213 million at December 31, 2018 and derivative assets of $301 million and derivative liabilities of $152 million at December 31, 2017. Gains (losses) on derivatives, net are predominantly included in trading revenue in the consolidated statement of income (loss).

[3] Gains (losses) on trading assets, excluding derivatives are included in trading revenue in the consolidated statement of income (loss).

[4] We are the client-facing entity and we enter into identical but opposite derivatives to transfer the resultant risks to our affiliates. With the exception of counterparty credit risks, we are market neutral. The corresponding intra-group derivatives are presented as equity derivatives and foreign exchange derivatives in the table.